Set default display units as px in svg icons

Also, remove Gnome template layer from small icons and fill the license
field.

contrib/icons/dosbox-staging.svg

@@ -14,7 +14,7 @@
    viewBox="0 0 33.866666 33.866666"
    version="1.1"
    id="svg5155"
-   sodipodi:docname="dosbox-staging-icon.svg"
+   sodipodi:docname="dosbox-staging.svg"
    inkscape:version="0.92.4 (unknown)">
   <defs
      id="defs5149" />
@@ -25,17 +25,17 @@
      borderopacity="1.0"
      inkscape:pageopacity="0.0"
      inkscape:pageshadow="2"
-     inkscape:zoom="11.2"
+     inkscape:zoom="2"
      inkscape:cx="39.770135"
      inkscape:cy="66.829441"
-     inkscape:document-units="mm"
+     inkscape:document-units="px"
      inkscape:current-layer="layer3"
      showgrid="true"
      units="px"
      inkscape:pagecheckerboard="true"
-     inkscape:window-width="1920"
-     inkscape:window-height="1016"
-     inkscape:window-x="1920"
+     inkscape:window-width="1366"
+     inkscape:window-height="704"
+     inkscape:window-x="0"
      inkscape:window-y="27"
      inkscape:window-maximized="1"
      showguides="true" />
@@ -47,8 +47,25 @@
         <dc:format>image/svg+xml</dc:format>
         <dc:type
            rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
-        <dc:title />
+        <dc:title></dc:title>
+        <cc:license
+           rdf:resource="http://creativecommons.org/licenses/by-sa/4.0/" />
       </cc:Work>
+      <cc:License
+         rdf:about="http://creativecommons.org/licenses/by-sa/4.0/">
+        <cc:permits
+           rdf:resource="http://creativecommons.org/ns#Reproduction" />
+        <cc:permits
+           rdf:resource="http://creativecommons.org/ns#Distribution" />
+        <cc:requires
+           rdf:resource="http://creativecommons.org/ns#Notice" />
+        <cc:requires
+           rdf:resource="http://creativecommons.org/ns#Attribution" />
+        <cc:permits
+           rdf:resource="http://creativecommons.org/ns#DerivativeWorks" />
+        <cc:requires
+           rdf:resource="http://creativecommons.org/ns#ShareAlike" />
+      </cc:License>
     </rdf:RDF>
   </metadata>
   <g